Capless lamps



J. ENGELEN Feb. 13, 1968 CAPLES S LAMPS Filed March 22, 1965 lnvenlor J'. EN ELEN,

y Mum/1, Wm.

United States Patent 3,369,144 CAPLESS LAMPS Jacobus Engelen, Weybridge, Surrey, England, assignor to Rival Lamps Limited, a British company Filed Mar. 22, 1965, Ser. No. 441,764 3 Claims. (Cl. 313-318) ABSTRACT OF THE DISCLOSURE A low voltage capless electric lamp having an envelope comprising'a globe portion and a neck formed with circumferentially extending ribs, a filament within the envelope and lead-in wires extending from the filament through the neck below the ribs, and bent back over the ribs.

This invention relates to low voltage capless electric lamps of the kind which are commonly used in motor vehicles, aircraft and instruments. The advantage of capless lamps over the more conventional capped lamps is the saving in the cost of providing the caps and assembling them accurately on the lamp envelopes. It is important that this saving of expense should not be lost by making the design of the lamps more complicated in other respects so that an unnecessary large number of additional manufacturing steps are necessary. It is accordingly the object of the invention to devise a lamp which utilises as far as possible the conventional lamp making machines and techniques.

In accordance with the present invention a capless lamp has a blow moulded glass envelope with a tubular neck which has been formed at each of two angularly spaced positions during the blow moulding operation with an outwardly projecting rib part extending around the circumference of the neck, a closed glass tube sealing the end of the neck, and a filament supported in the envelope by two lead-in wires which extend out through the sealed neck and are arranged so that they can be bent back one over each of the rib parts.

With this arrangement the lamp can be made in exactly the same way as a conventional lamp, which is formed by blow moulding and has its neck sealed with a glass tube, except that during the blow moulding operation rib parts are formed in the neck and, instead of fitting the ends of the lead-in wires in a cap, they are bent back over the rib parts.

The invention is applicable to the kind of lamp, for example, in which the closed glass tube is of smaller cross section than the neck and extends longitudinally through the neck into the envelope. The outer end of the tube is provided with an annular flange which is fused to the end of the neck and the other end of the tube is fused solid. The lead-in wires for the or each filament pass into the envelope through the tube and through the fused inner end of the tube. The envelope may be evacuated or gasfilled through a smaller tube which extends longitudinally through the first tube within the neck and communicates with the interior of the envelope through a hole in the solid end of the first tube. The outer end of the second smaller tube is fused solid to seal the envelope. This kind of lamp is commonly used for double filament motor vehicle headlights or stop/tail lights.

However the invention is particularly suitable to the simpler type of lamp in which the closed tube is the fused end of a tube which has been butt jointed to the end of 3,369,144 Patented Feb. 13, 1968 the neck and through which the envelope has previously been evacuated, or evacuated flushed out and filled with gas under pressure. In this case the lead-in wires pass out of the envelope through the butt seal.

The rib parts on the neck of the envelope may be quite discrete from one another or may be the different portions of a continuous rib extending part way or all the way around the circumference of the neck. In any case, the rib parts preferably extend around the circumference of the neck in a direction perpendicular to the axial length of the neck and at the same position along the length of the neck.

The lamp is intended to be used with a lampho'lder having a pair of spring contacts between which the neck of the bulb is a push fit with the lead-in wires trapped between the rib parts and the spring contacts. Not only do the rib par-ts serve the function of ensuring good electrical contact between the lead-in wires and the spring contacts of the holder but they enable the bulb to be held more positively within a holder of which the spring contacts are shaped so as -to engage behind the rib parts. When the lamp has only -a single filament, its two lead-in wires will overlie the rib parts on opposite sides of the neck. However, if the lamp is, for example, for a motor vehicle stop/tail light, with two filaments the three or four leadin wires will preferably be spaced at equal intervals around the neck and the corresponding rib parts will cooperate with the necessary contacts in a holder for the lamp.

One example of a lamp constructed in accordance with the present invention is illustrated in the accompanying drawings in which:

FIGURE I is a side elevation from one angle;

FIGURE II is a side elevation in the direction of the arrow II in FIGURE I; and,

FIGURE HI is an underneath plan view.

The lamp has a blow moulded glassenvelope consisting of a spherical globe 1 and a tubular cylindrical neck 2 with outwardly projecting rib parts 3 and 4 constituting a discontinuous annular rib extending around the neck. A conventional coiled tungsten filament 5 is supported in the globe 1 between the ends of two lead-in wires 6 and 7. The lead-in wires 6 and 7 are rigidly interconnected below the filament 5 by means of a conventional insulating glass bead 8 and extend side by side through the neck 2 and pass out of the envelope at diametrically opposite positions through a butt seal between the end of the tubular neck 2 and the collapsed stub 9 of an exhaust tube which has been fused to the neck to and through which the envelope has been evacuated during assembly in the conventional manner. The free ends 10 and 11 of the leading wires 6 and 7 respectively are bent back so that they lie along the outer surface of the neck 2 one overlying each of the projecting ribs 3 and 4. When the lamp is pressed into a suitable holder having diametrically opposite spring contacts, the tails 10 and 11 of the lead-in wires are trapped between the rib parts 3 and 4 and the spring contacts.

I claim:

1. A capless lamp having a blow moulded glass envelope comprising a globe a tubular neck below said globe which has been formed at each of two circumferentially spaced positions during the blow moulding operation with an outwardly projecting rib part extending circumferentially of the neck, a closed glass tube sealing the end of the neck, and a filament supported in the envelope by two lead-in wires which extend out through the sealed 3 neck below said rib part and are bent back over each of the rib parts.

2. A lamp according to claim 1, in which the closed tube is the fused end of a tube which has been butt jointed to the end of the neck and through which the envelope has previously been evacuated or evacuated, flushed out and filled with gas under pressure, the lead-in wires passing out of the envelope through the butt seal.

3. A lamp according to claim 1 or claim 2, in which the rib parts extend around the circumference of the neck in a direction perpendicular to the axial length of the neck and at the same position along the length of the neck.

References Cited UNITED STATES PATENTS Donovan 3133 18 X Clemen-ce 3'13-27 1 Foote 3l3-315 X Muller 313-315 X Howles 313318 Mever Q. 313--318 10 JOHN W. HUCKERT, Primary Examiner.

A. J. JAMES, Assistant Examiner. 

